linux-kernel - Re: [PATCH 2/3] scsi: libiscsi: fix invalid pointer dereference in iscsi_eh_session

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Message-ID: <2863c857-7121-1e96-0c28-d7f697b99ef7@sangfor.com.cn>
Date:   Sat, 11 Sep 2021 17:52:01 +0800
From:   Ding Hui <dinghui@...gfor.com.cn>
To:     Mike Christie <michael.christie@...cle.com>, lduncan@...e.com,
        cleech@...hat.com, jejb@...ux.ibm.com, martin.petersen@...cle.com,
        open-iscsi@...glegroups.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] scsi: libiscsi: fix invalid pointer dereference in
 iscsi_eh_session_reset

On 2021/9/11 12:38 上午, Mike Christie wrote:
> On 9/9/21 8:02 PM, Ding Hui wrote:
>> like commit 5db6dd14b313 ("scsi: libiscsi: Fix NULL pointer dereference in
>> iscsi_eh_session_reset"), access conn->persistent_address here is not safe
>> too.
>>
>> The persistent_address is independent of conn refcount, so maybe
>> already freed by iscsi_conn_teardown(), also we put the refcount of conn
>> above, the conn pointer may be invalid.
> 
> This shouldn't happen like you describe above, because when we wake up
> we will see the session->state is ISCSI_STATE_TERMINATE. We will then
> not reference the conn in that code below.
> 
> However, it looks like we could hit an issue where if a user was resetting
> the persistent_address or targetname via iscsi_set_param -> iscsi_switch_str_param
> then we could be accessing freed memory. I think we need the frwd_lock when swapping
> the strings in iscsi_switch_str_param.
> 

Thanks for your detailed explanation, I'll drop 2/3 and 3/3 in v2 patch.
I expect that the persistent_address issue be fixed in your future patchset.

Sorry for my ignorance.

> 
>>
>> Signed-off-by: Ding Hui <dinghui@...gfor.com.cn>
>> ---
>>   drivers/scsi/libiscsi.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
>> index 712a45368385..69b3b2148328 100644
>> --- a/drivers/scsi/libiscsi.c
>> +++ b/drivers/scsi/libiscsi.c
>> @@ -2531,8 +2531,8 @@ int iscsi_eh_session_reset(struct scsi_cmnd *sc)
>>   	spin_lock_bh(&session->frwd_lock);
>>   	if (session->state == ISCSI_STATE_LOGGED_IN) {
>>   		ISCSI_DBG_EH(session,
>> -			     "session reset succeeded for %s,%s\n",
>> -			     session->targetname, conn->persistent_address);
>> +			     "session reset succeeded for %s\n",
>> +			     session->targetname);
>>   	} else
>>   		goto failed;
>>   	spin_unlock_bh(&session->frwd_lock);
>>
> 


-- 
Thanks,
-dinghui